COSTA DEL GOALS: Diego Costa has hit the ground running in the Premier League [GETTY]

The summer signing from Atletico Madrid scored Chelsea's opening goals in their victories against newly-promoted Burnley and Leicester.

And against an Everton side expected to provide a tougher test, the prolific Spaniard did it again.

On the day Mourinho finally got rid of £50m misfit Fernando Torres, new-boy Costa took just 35 seconds to fire Chelsea on the way to a win that lifted them top of the league.

And he wrapped up a thrilling win with his second in the final minute of normal time.

Despite former Chelsea striker Samuel Eto'o coming off the bench in the second half to pull Everton back into the game with his first goal for the club, Mourinho's men proved their credentials with a third straight win.

There had been doubts over the fitness of Costa after he picked up a hamstring injury in training in midweek. There had even been fears he could be sidelined for up to six weeks.

But he blew those worries away by catching Everton's defence cold after just 35 seconds.

It was quick thinking from another summer arrival, Cesc Fabregas, which sliced up the home side's static back line.

The pass gave Costa the edge and he whipped his shot across World Cup hero Tim Howard.

The Toffees were visibly stunned but there was so much worse to follow as Branislav Ivanovic forced Howard to pick the ball out the net again just two minutes later.

Everton's defenders screamed for offside but Ramires played on to slip Ivanovic through and he converted.

It was 15 minutes before Everton managed a shot on the visitors' goal as Chelsea threw men behind the ball to protect a lead they hoped would be enough to take them top of the table.

If Chelsea were happy to defend their lead, Everton seemed just as content not to expose themselves at the back too often in the pursuit of a way back into the match.

But just as Everton had been caught asleep at the start of the first half, so Chelsea were caught napping as referee Jon Moss was about to blow for half-time.

Seamus Coleman floated a ball into the box which should have been hoofed back from where it came. Instead, Mirallas climbed between Gary Cahill and John Terry to head beyond Thibaut Courtois.

While there had been periods of stalemate before the break, the goals came thick and fast after the restart.

Eden Hazard forced a 67th-minute shot in off Coleman as Howard grasped for the ball.

Chelsea were not having it all their own way and in-form Scot Steven Naismith showed again his new-found confidence under Martinez by powering clear to pull a goal back just two minutes later.

Nemanja Matic thought he had put the clash beyond the spirited home side just four minutes later with a long-range effort that spun through a ruck of legs to drift past Howard.

But Eto'o had other ideas, taking just six minutes after coming off the bench to head firmly past Courtois in the 75th minute.